Gyroscopic compass



G. B. HARRISON AND A. L. RAWLINGS.

GYROSCOPIC COMPASS.

APPLICATION FILED AUG-9. I919.

1 3 g g Patented Dec. 21, 1920.

2 SHEETS-SHEET I. 1

5 l WEI? V /LX\ y G. B. HARRISON AND A. L. RAWLINGS.

eYRoscoPlc COMPASS.

APPLICATION FILED AUG.9, I919. 1,362,941.11 Patented Dec. 21, 1920.

2 SHEETS-SHEET 2.

I IP EJIG UNITED STATES PATENT OFFICE.

ENGLAND, ASSIGNORS TO THE SPERRY GYROSCOPE COMPANY, OF BROOKLYN,

NEW YORK.

GYROSCOPIC COMPASS.

Specification of Letters Patent. Pate t d D 21; 1920 Application filed August 9, 1919. Serial No. 316,484.

T 0 all whom it may concern:

Be it known that we, GEOFFREY BRANCKER HARRISON and ARTHUR LIONEL RAWLINGS, both subjects of the King of Great Britain, residing at Admiralty Compass Observatory, Slough, in the county of Buckingham, England, have invented certain new and useful Improvements in Gyroscopic Compasses,. of which the following is a specification. I

The invention relates to gyro compasses and more particularly to compasses which are not pendulous, or at least not sufficiently so to impart meridian seeking properties thereto, but in which meridian seeking properties are largely obtained by causing a flow of liquid between the north and south sides of the gyro when the spinning axis of the gyro is tilted.

Compasses approaching this principle have already been proposed in which the flow is caused by an air blast controlled by a valve operated by the tilting of the gyro casing. It has also been proposed to use a level connected to the gyroscope by a yielding attachment and capable of movement relatively thereto, in order to exert a controlling torque on the gyroscope.

In such compasses also liquid has been forced to the high side of the gyroscope by the air blast so that the compass behaves as an ordinary pend'ulous gyroscope.

In either of these arrangements when the compass in carried in a rolling ship the liquid is liable to surge from side to side and introduce torques around the vertical axis of the compass, resulting in deviations when the ship is not on'a cardinal course. It has been proposed to prevent this surg ing by using a viscous fluid and a capillary tube or constriction in the level, but this prevents the compass from having a correct ballistic deflection on change of speed in latitude, which results in oscillations of the compass in azimuth after alterations in the course or speed ofthe ship and which also interferes with the meridian seeking properties'of the compass.

In the present invention, which is equally applicable whether the liquid or other laterally movable mass is forced to the higher side of the gyroscope or flows by gravity to the lower side, but in employing which I prefer and have illustrated the latter embodiment. Novel means is employed to pre- I -arranged on the gyroscope that the liquid has a natural period of oscillation between north and south very different in period and preferably greater than the longest pellOCl of roll of the ship, so that synohronism between the two is never maintained for any appreciable time.

It is known that in the case of a common U tube containing a column of liquid of uniform cross section, the period of oscillation of the liquid (neglecting friction) is proportional to the square root of the length of the column. To obtain the period required in a gyro compass with a uniform column of liquid would involve an inconveniently long tube, but by making the U tube bell mouthed or terminating in boxes or enlarged ends of suitable type so that the cross sectional area at the ends of the column is greater than that of the connecting portion, the period of oscillation can be increased in the ratio of these two areas. In addition to this, there is in practice a considerable lengthening of the period due to friction of the liquid in the pipeso that the period may easily be lengthened to infinity, when the motion becomes dead-beat. In applying this to the compass, two boxes and a connecting pipe form the equivalent of a bell-mouthed U-tube and In consequence ofthis long period the disturbance of the liquid due to rolling of the ship is reduced to a very small amount, and further it is made to differ in phase by about a quarter period from the disturbing force. When the ship is rolling .on an intercardinal or other course there is therefore no persistent torque around the vertical axis of the compass to cause deviation.

At the same time the period of oscillation of the liquid is not so slow as to make the it has been thought necessary to provide a separate and distinct damping means for the gyroscope operating to transfer a separate supply of liquid out of phase with the principal mass of the liquid. We have found, however, that such complications may be entirely eliminated by mounting the liquid container in such a manner as to bring into action the damping torque whenever the liquid in the two containers becomes unbalanced. By this means a compass of extreme simplicity is produced employing no extraneous forces or elements other than the usual follow-up system. and force of gravity.

In order that the said invention may be clearly understood and readily carried into efi'ect, we'will describe the same more fully with reference to the accompanying drawings, in which Figure 1 is a north elevation partly in,

section of a compass embodying this vention.

Fig. 1 is a sectional detail view of a liquid box.

Fig. 2 shows part of the compass in east elevation.

Fig. 3 is a detail viewshowing one method of connecting an arm from the gravity controlling devic to the gyro casing; and a Figs. 4 and 5 shosv another method of connection.

Fig. 6 is a detail view of an indicator.

The gyro, which is preferably electrically driven in the ordinary way, is contained in the casing 1, supported in a Vertical gimbal ring 2 by the horizontal trunnions 5, 5. This vertical ring 2 is itself supported in a phantom or follow-up element 3 by the vertical bearings 6, 6; this phantom element carries the card 4-. and is electrically'power driven in the well known manner'employed in the type of compass shown in the Sperry Patent 1,279,471 of September 17 1918, so as to maintain its plane coincident with the plane of the vertical ring 2. To this end the motor is controlled by pairs of contacts 7 inclination carried on the vertical ring and phantom element respectively, making a follow-up system of the usual kind. I

Supported by horizontal bearings 10, 10 in the phantom ring 3 is a framework 9 carrying two boxes 8, 8. This frame is connected to the gyro case 1 by the arm 11 and a flexible joint 12 which may take the form of a roller, link or spring; this flexible joint allows the frame 9 to have a small movement in azimuth relatively to the case 1 but obliges the case and frame to tilt together around the axes 5, 5, and 10, 10 respectively, these two axes lying normally in one straight line.

One form of this flexible joint is shown .in Fig. 3, WhGIGuI roller 12 is pivoted on the arm 11 and engages with a channel piece 14 fixed to the bottom of the gyro case 1. The groove of the channel is parallel to the plane of the gyro wheel and is of the same width as the diameter of the roller so as to allow free relative movement in azimuth between the gyro case and the arm 11 but no relative tilting movement.

An alternative form of this flexible joint is shown in Figs. 4: and 5 in elevation and plan. In this case the connection is made by a flat ribbon spring 15, such as a short length of clock spring, with its plane vertical. One end of the spring is connected to the case 1 and the other end to the arm 11. The spring is stiff enough to obliga these two parts to tilt together but is sufficiently flexible to allow of a small relative movement in azimuth.

The boxes 8, 8 are about half filled with oil, mercury or other liquid and their bottoms are connected by a pipe 13 so that when the frame 9 is tilted the liquid may flow by gravity from thehigher box to the lower. As long as the compass is horizontal, however, no torque is applied by the liquid. As

' soon, however, as the compass becomes inclined, due to the rotation of the earth, the liquid running to the low side of the compass .will exert a torque around the horizontal axis thereof. Even though only a comparatively small quantity of liquid is transferred it will exert an appreciable torque on the compass owing to the long lever arm equal to the distance of the. axis 10 from either container 8 so that even when off the meridian and inclined the compass.

principles that the level of the liquid may be practically undisturbed by the rolling of the ship and will respond only to the longer period accelerations due to change of speed and latitude to give the required ballistic deflection. The compass, therefore, having no unbalanced or pendulous element connected thereto remains unaffected by the rolling and pitching of the ship since deflectionof gyro compasses as constructed prior to our invention has been found to be due substantially entirely to the acceleration pressures acting on a pendulously supported element connected to or forming a part of the gyroscope or sensitive element. j

Owing to the variation in the speed error in different latitudes the-ballistic deflection is required to have a greater value in high latitudes than in positions near the equator. It has been the practice, hitherto, to design gyro compasses so that the ballistic deflection may be of the correct amount in.some single mean latitude, leaving a residual uncorrected error in all other latitudes.

Under unfavorable circumstances, when the ual error causes a serious temporary deviation of the compass.

In the present gyro compass, therefore, an adjustment is embodied by which the correct ballistic deflection may be obtained in any navigable latitude. The amount of the ballistic deflection depends, in this case, upon the area of the horizontal cross-section of the boxes, 8, 8 containing the liquid.

The area is made variable by any convenient means. In the particular method shown in Fig. 1 the box 8 is divided by the partitions 16 into a number of separate chambers 17 (three chambers are shown) of different sizes and communication between the tubes 13 and any one, two or three of such chambers is controlled by the cock or valve 18 provided with a milled head 19 by which it can be turned from outside. The chambers 17 to be employed for any given latitude are determined in accordance with the characteristics of the compass and the necessary adjustments of the valve 18 are made as occasion requires. With proper adjustment the ballistic deflection after any change of speed or course may be made equal to the difference between the error due to the speed and course preceding the change and the error due to the new speed and course subsequent to the change. The compass then moves practically dead beat to the new settling position on change of speed or course, without oscillation in azimuth.

The compass is caused to seek the meridian by the couple about the horizontal axis due to the preponderance of liquid in one of the boxes 8, whenever the gyro axle is 'wise as seen from the north side.

The damping is effected by an extremely simple expedient and without the employment of any additional or extraneous means whatever. For this purpose. the frame 9 is connected to the gyro case at a point 12 which is a little to the east of the center of the gyro. The couple given by the frame 9 and boxes 8 therefore acts in a plane which is not entirely vertical and the component in the horizontal plane causes the gyro to precess so as constantly to reduce its tilt at a rate depending on the tilt itself. Such a damper is only brought into action by the means imparting meridian seeking properties to the gyroscope, which being normally non-pendulous or substantially so is unaffected by the rolling and pitching of the ship as hereinbefore explained. v

In order to enable the tilt of the gyroscope to be measured so as to aflord an indication of the deviation of the compass, a small piston 20 may be provided to slide in the pipe 13 which connects the bottqms of the two boxes 8. The pipe may be of glass, and graduated as indicated by graduations 21 which cooperate with index 22 on the piston so that, as the piston is moved along by the liquid, its position indicates the tilt of the gyro axis. As the liquid is substantally undisturbed by the rolling of the ship, the position of the piston is similarly undisturbed, which is not the case with a spirit level.

What we claim and desire to. secure by Letters Patent of the United States is 1. In a gyroscopic compass of the type referred to, the combination with a gyroscope casing, of a follow up member surrounding the gyroscope casing, and a liquid containing vessel pivotally supported upon said follow up memberand adapted to give a indicator arranged within the tube and moving with the liquid, for the purpose specified.

5. In a gyroscopic compass of the type referred to, the combination with a gyroscope casing, of means for permitting the transfer of liquid from one side of an axis of said casing to another, including a liquid container and adjustable means associated with said container for regulating the mass of liquid causing ballistic deflection according to the latitude of the location of the compass.

6. In a gyroscopic compass, the combination with a gyroscope casing, of means for transferring liquid from one side of an axis of said casing to another including two containing vessels and a duct connecting them,

the form of said vessels being such that the ends of the liquid column are of larger cross sectional area than the intermediate connecting body, and means by which the effective cross sectional area of the ends of the liquid column in the two vessels may be adjusted.

7. In a gyroscopic compass, thecombination with a gyroscope casing, of means for transferring liquid from one side of an axis of said casing to another includingv two containing vessels and a duct connecting them, the form of said vessels being such that the ends of the liquid column are of larger cross sectional area than the intermediate connecting body, partitions dividing the liquid vessels into a plurality of chambers, and means for shutting off liquid confined by one or more of said partitions from the main body of liquid.

8. In a gyroscopic compass, the oombination with a gyroscope, casing, of means for transferring liquid from one side of an axis of said casing to another including two containing vessels and a duct connecting them, theform of said vessels being such that the ends'of the liquid column are of larger cross sectional area than the-intermediate connecting body, partitions dividing the liquid vessels into a plurality of chambers, and a controlling valve adapted to place the duct connecting the vessels in communication with any desired number of said chambers.

9. In a gyroscopic-compass, the combinationwith a gyroscope, of means for mounting the same near its center of gravity for oscillation about a horizontal axis, and for scaeao tion with a gyroscope caslng and means for v mounting the same for oscillation about a horizontal axis and turning about a vertical axis, of a follow-up member constrained to follow the movements of said casing about the vertical axis, means for imparting directive power to said casing comprising a mass movable laterally with respect to said horizontal axis on inclination of said casing and supported on said follow-up member, said mass being connected to said casing about an axis inclined to the horizontal.

11. The combination with a gyroscopic compass having a gyroscope and means for supporting the same in substantially neutral equilibrium about a horizontal axis, of a container mounted at each side of the axis of said gyroscope and adapted to contain a liquid, a connection permitting interchange of liquid between said containers, said containers being also connected to said gyroscope to exert a torque thereon about both a horizontal and a vertical axis as the liquid flows from one container to the other.

12. In a gyroscopic compass, the combination with a gyroscope casing and means for mounting the same for oscillation about a horizontal axis and turning about a vertical axis, of a follow-up member constrained to follow the movements of said casing about the verticalaxis, means for impartmg directive power to said casin comprising a mass freely movable lateral y with respect to said horizontal axis on inclination of said casing and supported on said follow-up member, said mass being connected to said casing about an axis inclined to the horizonta 13. In a gyroscopic compass of the type referred to, the combination with a gyroscope casing, of a follow-up member surrounding the gyroscope casing, and a li uid containing vessel pivotally supporte upon said follow-up member and having a connection with said casing to impart meridian seeking properties thereto.

14. The combination with a gyroscopic A.

compass mounted for oscillation about a horizontal axis, of means for imparting directive power'thereto comprising a mass freely movable laterally with respect to said axis so as to cause a gravitational torque to I be applied thereon on inclination of the gyroscope, and adjustable means for varying the weight of said movable mass whereby the properdefiection of the compass for difii'erent latitudes may be obtained.

15'. In a gyroscopic compass, the combination with a gyroscope casing, of means for transferring liquid from one side of an axis of said casing to another including two containing vessels and a duct connectin them, the form of said vessels being such t at the ends of the liquid column are of larger cross sectional area than the intermediate connecting body, and-adjustable means for varying the quantity of liquid having communication with both vessels.

16.In a gyro-compass, the combination witha rotating wheel and means for mounting the same in substantial equilibrium for oscillation about a horizontal axis and turnin about a vertical axis, of laterally shiftab le means for imparting directional or meridional seeking properties thereto and i said axes.

18. In a gyro-compass, the combination with a rotating wheel and means for mounting the same in substantial'equilibrium for oscillation about a horizontal axis and turning about a vertical axis, of normally nonpendulous means for imparting directional or meridional seeking'properties thereto and means for damping. the/ oscillations thereof about either or both of said axes, said damping means being brought into action by said first named means.

19. In a gyro-compass, 'the combination with a rotatin Wheel and means for mounting the same 1n substantial equilibrium for oscillation about a horizontal axis and turning about a vertical axis, of normally nonpendulous means responsive to the inclination of said wheel for imparting directional or meridional seeking properties thereto and for damping the oscillations thereof about either or both of said axes, said damping means being brought into action by said first named means 20. In a ro-compass, the combination with a rotating wheel and means for mounting the same 1n substantial equilibrium for oscillation about a horizontal axis and turning about a vertical axis, of independently supported normally non-pendulous means, for imparting directional or meridional seeking properties thereto, and a connection between said means and wheel of such a character as to damp the oscillations of the compass.

GEOFFREY BRANCKER HARRISON.

ARTHUR LlONEl. RAWLINGS. 

